The present invention relates to a composite magnetic head for use in magnetic disk drives, and more particularly to a composite magnetic head for use in magnetic disk drives having increased linear recording densities.
A composite magnetic head has a structure generally shown in FIG. 1, and a magnetic core for constituting a main magnetic circuit is shown in FIG. 10. The magnetic head 1 comprises a magnetic core 2 constituted by a pair of magnetic core pieces 4, 4 both made of an oxide-type magnetic material and bonded to each other via a magnetic gap 6. At least one of the magnetic core pieces 4, 4 is provided with a thin, magnetic metal layer 5 produced by a sputtering method, etc. on a surface facing the magnetic gap 6 of the magnetic core 2. This thin, magnetic metal layer 5 is usually made of a soft magnetic material based on an Fe--Al--Si alloy.
With respect to such a magnetic head having a thin, magnetic metal layer, Japanese Patent Laid-Open No. 59-160811 discloses a thin, magnetic metal layer whose columnar crystals are oriented substantially in perpendicular to a sliding surface of a magnetic recording medium. However, this orientation of the columnar crystals fails to provide the magnetic head with a sufficient performance.
Japanese Patent Laid-Open No. 61-110309 discloses a magnetic head provided with a thin, ferromagnetic metal layer having a columnar crystal structure whose orientation is substantially in perpendicular to a magnetic gap-facing surface. However, this reference fails to teach the specific structures of the columnar crystals and their effects on the performance of the magnetic head.
In such a composite magnetic head, it is known that a self-reproduced waveform suffers from noises, and that such noises are likely to cause errors in recent magnetic recording apparatuses comprising magnetic recording media having extremely increased linear recording densities.
FIG. 2 shows a waveform in the reproduction of a single pulse signal. The maximum output voltage is obtained at a position corresponding to the magnetic gap of the magnetic head, and a signal called "secondary gap pulse" (indicated by "B") is observed at a position corresponding to a boundary between the thin, magnetic metal layer and the magnetic core piece made of an oxide-type magnetic material, due to the difference in magnetic properties between them. Between the maximum output voltage peak and the secondary gap pulse B corresponding to the position of the thin, magnetic metal layer, there is a noise observed as a fluctuation (indicated by "A") of a waveform. This fluctuation has been considered to cause problems.